1. Field of the Invention
The present invention relates to a method and device for recognizing in a communication signal the audio signatures of dialing pulses corresponding to a dialed digit. The invention also extends to a method and device for converting into a tone frequency signal a series of dialing pulse signatures to thereby enable a caller to adequately control by pulse dialing a remotely controllable equipment connected to a telephone line.
2. Brief Description of the Prior Art
Most of the equipements remotely controllable through the telephone network operates satisfactorily only with DTMF (Digital Tone Modulation Frequency) tone dialing, that is Touch-Tone (trademark) dialing. With DTMF tone dialing, each digit dialed produces on an already established telephone connection a tone having a predetermined, associated frequency which can be recognized by the remotely controllable equipement. After the caller has reached the desired subscriber's telephone number, he has only to depress one or many push buttons of his telephone set and the remote controlled equipement recognizes the so produced tones to perform the desired operation, in particular but not exclusively to establish a line connection between the caller and a given person or service.
With pulse dialing, each digit dialed produces one pulse (digit 1) or a series of pulses (digits 2-0) on an already established telephone connection. This is the case for example with telephone sets comprising a conventional rotating dial. The pulses are produced by closing and opening the loop formed by the telephone line of the caller and the pulses are therefore not transmitted beyond the first telephone station. Beyond that station, only the noise, that is the audio signature of each pulse, is propagated. As this signature somewhat varies from one pulse to the other, it is not trivially recognizable by remotely controllable equipements.